Victor: Something seems to have changed in the last few days.  When I merged, both specific classes
python -m test -R 3:3 -u gui -v test_idle -m idlelib.idle_test.test_configdialog.FontPageTest.*
and the module as a whole passed.
python -m test -R 3:3 -u gui -v test_idle -m idlelib.idle_test.test_configdialog.*.*

Today, not having touched configdialog or test_configdialog, test_configdialog as a whole passes but FontPageTest, IndentTest, and GenPageTest fail with 
test_idle leaked [1, 1, 1, 1] memory blocks, sum=4
(Tested individually, VarTraceTest and the empty HighlightTest pass.)
I presume that cleanUpModule still runs with the restriction.

Could any of your other recent changes to regrtest have introduced a spurious 1 block error when tests are filtered?